ZNSE-BASED MBE-GROWN PHOTODIODES

ZnSe p-i-n-type photodiodes were grown on GaAs substrates using molecu lar beam epitaxy technique. ZnCl2 was used for n-doping and plasma-exc ited N-2 for p-doping. The p-side contact consists of 200 nm Au in sit u deposited on a 20 nm highly doped ZnTe layer on top of the p-doped Z nSe forming a well-defined Schottky barrier, as can be confirmed by cu rrent-voltage measurements together with an electrical model of the di ode. Reverse-bias photocurrent was measured as a function of wavelengt h. The spectral responsivity is about 30 mA/(WeV) at the band edge whi ch corresponds to a quantum efficiency of roughly 8%. Calculations of the spectral response were performed using a modified model originally designed on Si solar cells and reflectivity data determined by ellips ometry. The comparison of the model with measurements indicates that t he photocurrent is dominated by the drift current generated within the space-charge region. (C) 1998 Published by Elsevier Science B.V. All rights reserved.